The present disclosure relates to transport of print media and particularly print media in sheet form as is employed in photocopiers and office printers. The disclosure particularly relates to digital image printing in print engines arranged for parallel processing, as for example, printing in plural print engines and for duplex printing on both sides of a print media sheet.
In print engines arranged for parallel processing, it is often the case that the transport of sheet print media will by-pass one or more print engines in order to print concurrently on another print engine. However, the transport path must also include a provision for reversing the direction and movement of the sheet print media for duplex printing. Thus, the transporters propelling the sheets for moving the sheet print media through the designated path must provide for bi directional movement. Heretofore, such bi directional print sheet media movement has been provided by individual transporters disposed in the media path with one transporter arranged to provide print sheet media movement in a forward direction such as for bypass and simplex printing, and another transporter disposed to arrange for print sheet media movement in the reverse direction such as for duplex printing. The transporters are typically each comprised of a series of nip rollers driven by a belt powered by an individual single direction of rotation drive motor. Thus, the functionality of bi directional print sheet media movement in a print engine has been somewhat complex and costly because of the need for plural print sheet media transporters.
It has therefore been desired to reduce the complexity and cost of a sheet transport digital print engine arrangement for parallel printing employing bypass capability and providing for duplex printing on opposite sides of print sheet media.